1. Technical Field
The present invention relates to a method for producing and using an engine component, in particular a piston for an internal combustion engine, in which an aluminium alloy is cast using the gravity die casting method, an engine component consisting at least partially of an aluminium alloy, and the use of an aluminium alloy to produce such an engine component.
2. Related Art
In recent years, there has been a growing demand for particularly economical and thus ecological means of transport, which have to meet high consumption and emission requirements. There is furthermore always the need to design engines to be as high performance and as low in consumption as possible. Pistons that can be used at increasingly higher combustion temperatures and combustion pressures, which is essentially made possible by increasingly higher performance piston materials, are a decisive factor in the development of high-performance and low-emission internal combustion engines.
A piston for an internal combustion engine fundamentally has to have a high heat resistance and must at the same time be as light and firm as possible. Thereby of particular importance is how the microstructure distribution, the morphology, the composition and the thermal stability of highly heat-resistant phases are configured. An optimisation in this regard normally takes into consideration a minimal content of pores and oxide inclusions.
The sought-after material must be optimised both as regards isothermal fatigue strength (HCF) and as regards thermomechanical fatigue strength (TMF). In order to optimally configure the TMF, the finest possible microstructure of the material should always be strived for. A fine microstructure reduces the risk of the occurrence of microplasticity or microcracks at relatively large primary phases (in particular at primary silicon precipitates) and thus also the risk of crack initiation and crack growth.
Under TMF stress, microplasticities and/or microcracks, which can considerably reduce the lifespan of the piston material, occur at relatively large primary phases, in particular at primary silicon precipitates, owing to the different coefficients of expansion of the individual components of the alloy, namely the matrix and the primary phases. In order to increase the lifespan, it is known to keep the primary phases as small as possible.
In the used gravity die casting, there is a concentration upper limit up to which alloy elements should be introduced, and if this limit is exceeded, the castability of the alloy is reduced or casting becomes impossible. Furthermore, at too high concentrations of strengthening elements the formation of large plate-like intermetallic phases occurs, which drastically reduce the fatigue strength.
DE 44 04 420 A1 describes an alloy that can be used in particular for pistons and for components which are exposed to high temperatures and are subjected to high mechanical stress. The described aluminium alloy comprises 8.0 to 10.0% by weight of silicon, 0.8 to 2.0% by weight of magnesium, 4.0 to 5.9% by weight of copper, 1.0 to 3.0% by weight of nickel, 0.2 to 0.4% by weight of manganese, less than 0.5% by weight of iron as well as at least one element selected from antimony, zirconium, titanium, strontium, cobalt, chromium and vanadium, with at least one of these elements being present in an amount of >0.3% by weight and the sum of these elements being <0.8% by weight.
EP 0 924 310 B1 describes an aluminium/silicon alloy that is used to produce pistons, in particular pistons in internal combustion engines. The aluminium alloy has the following composition: 10.5 to 13.5% by weight of silicon, 2.0 to less than 4.0% by weight of copper, 0.8 to 1.5% by weight of magnesium, 0.5 to 2.0% by weight of nickel, 0.3 to 0.9% by weight of cobalt, at least 20 ppm of phosphorus and either 0.05 to 0.2% by weight of titanium or up to 0.2% by weight of zirconium and/or up to 0.2% by weight of vanadium, with the rest being aluminium and unavoidable impurities.
WO 00/71767 A1 describes an aluminium alloy that is suitable for high temperature applications such as, for example, heavy duty pistons or other uses in internal combustion engines. The aluminium alloy is thereby composed of the following elements: 6.0 to 14.0% by weight of silicon, 3.0 to 8.0% by weight of copper, 0.01 to 0.8% by weight of iron, 0.5 to 1.5% by weight of magnesium, 0.05 to 1.2% by weight of nickel, 0.01 to 1.0% by weight of manganese, 0.05 to 1.2% by weight of titanium, 0.05 to 1.2% by weight of zirconium, 0.05 to 1.2% by weight of vanadium, 0.001 to 0.10% by weight of strontium, with the rest being aluminium.
DE 103 33 103 B4 describes a piston produced from an aluminium cast alloy, said aluminium cast alloy containing: 0.2 or less % by weight of magnesium, 0.05 to 0.3% by weight of titanium, 10 to 21% by weight of silicon, 2 to 3.5% by weight of copper, 0.1 to 0.7% by weight of iron, 1 to 3% by weight of nickel, 0.001 to 0.02% by weight of phosphorus, 0.02 to 0.3% by weight of zirconium, with the rest being aluminium and impurities. It is furthermore described that the size of a non-metal inclusion present within the piston is less than 100 μm.
EP 1 975 262 B1 describes an aluminium cast alloy consisting of: 6 to 9% of silicon, 1.2 to 2.5% of copper, 0.2 to 0.6% of magnesium, 0.2 to 3% of nickel, 0.1 to 0.7% of iron, 0.1 to 0.3% of titanium, 0.03 to 0.5% of zirconium, 0.1 to 0.7% of manganese, 0.01 to 0.5% of vanadium, and one or more of the following elements: 0.003 to 0.05% of strontium, 0.02 to 0.2% of antimony, and 0.001 to 0.03% of sodium, with the total amount of titanium and zirconium being less than 0.5% and aluminium and unavoidable impurities constituting the rest when the total amount is set at 100% by weight.
WO 2010/025919 A2 describes a method for producing a piston of an internal combustion engine, wherein a piston blank is cast from an aluminium/silicon alloy while adding proportions of copper and is then finished. The invention thereby stipulates that the proportion of copper amounts to a maximum of 5.5% of the aluminium/silicon alloy and that proportions of titanium (Ti), zirconium (Zr), chromium (Cr) and/or vanadium (V) are mixed into the aluminium/silicon alloy, and the sum of all of the components is 100%.
The application DE 10 2011 083 969 relates to a method for producing an engine component, in particular a piston for an internal combustion engine, in which an aluminium alloy is cast using the gravity die casting method, as well as to an engine component that consists at least partially of an aluminium alloy, and to the use of an aluminium alloy for producing an engine component. The aluminium alloy thereby comprises the following alloy elements: 6 to 10% by weight of silicon, 1.2 to 2% by weight of nickel, 8 to 10% by weight of copper, 0.5 to 1.5% by weight of magnesium, 0.1 to 0.7% by weight of iron, 0.1 to 0.4% by weight of manganese, 0.2 to 0.4% by weight of zirconium, 0.1 to 0.3% by weight of vanadium, 0.1 to 0.5% by weight of titanium, with the rest being aluminium as well as unavoidable impurities. This alloy preferably has a phosphorus content of less than 30 ppm.